Thin film transistor and method for manufacturing the same, array substrate, and electronic apparatus

ABSTRACT

A thin film transistor and a method for manufacturing the same, an array substrate including the thin film transistor, and an electronic apparatus including the thin film transistor or provided with the array substrate. The thin film transistor includes: a gate electrode, a gate insulating layer, an active layer, and a source electrode and a drain electrode, the active layer is formed of a mixture including a semiconductor nano-material and a photoresist material. The method for manufacturing the thin film transistor includes: preparing a mixture including a semiconductor nano-material and a photoresist material; applying the mixture over a substrate, and forming a patterned active layer by exposure and development.

FIELD OF THE INVENTION

Embodiments of the present invention relate to a thin film transistorand a method for manufacturing the same, an array substrate includingthe thin film transistor, and an electronic apparatus including the thinfilm transistor or provided with the array substrate.

BACKGROUND

As the displaying technology has been developing at a high speed, thinfilm transistor liquid crystal display (TFT-LCD) has dominated the fieldof the flat panel display. The TFT-LCD is also called Active MatrixLiquid Crystal Display (AMLCD). The TFT-LCD includes a plurality ofpixel units, and each of the pixel units is provided with a thin filmtransistor (TFT) for controlling displaying of the pixel units. Further,the display devices such as an active matrix/organic light emittingdiode (AMOLED) or the like and electronic apparatuses provided withX-ray detector also need a thin film transistor to achieve theirfunctions.

On the other hand, semiconductor nano-materials, such as semiconductornano-wire, semiconductor carbon nanotube, semiconductor grapheme, andthe like, have advantages of low manufacturing cost, scale production,and the like; furthermore, it is a semiconductor per se, if it isapplied in the TFT-LCD as an active layer of the TFT, the producing costof TFT-LCD can be reduced remarkably. However, the semiconductornano-material has a small size, for example, in general, nano-wire has awidth less than 100 nm, for another example, a grapheme has a size ofabout 1 μm, which is difficult to be arranged on the array substrate inorder. Nano-imprint or electric field distribution is not applicable inthe scale production of the TFT-LCD due to high processing cost.Therefore, it is difficult to apply the semiconductor nano-material inthe TFT-LCD to reduce producing cost of the TFT-LCD in the prior arts.

SUMMARY

According to embodiments of the present invention, a thin filmtransistor and a method for manufacturing the same, an array substrateincluding the thin film transistor, and an electronic apparatusincluding the thin film transistor or provided with the array substrate,are provided, thereby resolving the technical problem that it isdifficult to apply semiconductor nano-material to the display field.

To attain the object described above, the embodiments of the presentinvention adopt the following technical solutions:

According to an embodiment of the present invention, there is provided athin film transistor, comprising a gate electrode, a gate insulatinglayer, an active layer, a source electrode and a drain electrode,wherein, the active layer is formed of a mixture including asemiconductor nano-material and a photoresist material.

In one example, the semiconductor nano-material comprises one or moreselected from a group consisting of semiconductor nano-wire,semiconductor carbon nanotube and semiconductor nanoscale graphene.

In one example, the semiconductor nano-wire material is one or moreselected from a group consisting of cadmium sulfide, zinc oxide,silicon, cadmium, gallium nitride and indium phosphide.

In one example, the photoresist material is an electron beam photoresistof polymethylmethacrylate (PMMA) or a photosensitive polyimide (PI).

In one example, the mixture further includes a solvent, and thesemiconductor nano-material has a content of 1 mg/mL to 50 mg/mL,preferably 5 mg/mL to 30 mg/mL, more preferably 10 mg/mL to 20 mg/mL, inthe mixture.

In one example, a mass ratio between the semiconductor nano-material andthe photoresist material is 1:5 to 1:250, preferably 1:25 to 1:150, morepreferably 1:50 to 1:100.

In one example, the thin film transistor is a bottom gate type thin filmtransistor.

In one example, the gate insulating layer is located above the gateelectrode, the source electrode and the drain electrode are locatedabove the gate insulating layer and disposed on both sides of the gateelectrode, and the active layer is located above the source electrode,the drain electrode and the gate insulating layer.

In one example, the active layer has a flat surface.

Another embodiment of the invention provides an array substratecomprising the thin film transistor as mentioned above.

In one example, the array substrate comprises a base substrate, and thethin film transistor is provided on the base substrate.

In one example, the array substrate further comprises a pixel electrodeprovided above the base substrate, and the pixel electrode iselectrically connected with a drain electrode of the thin filmtransistor.

In one example, the thin film transistor is a bottom gate type thin filmtransistor, the gate insulating layer is located above the gateelectrode, the source electrode and the drain electrode are locatedabove the gate insulating layer and disposed on both sides of the gateelectrode, and the active layer is located above the source electrode,the drain electrode and the gate insulating layer, and the pixelelectrode is disposed directly on the active layer. In this case, thepixel electrode is electrically connected with the drain electrodethrough the active layer.

In one example, the array substrate further comprises a pixel defininglayer disposed on the gate insulating layer, and the pixel defininglayer is located around the pixel electrode.

In one example, a via hole is provided in the gate insulating layer, apart of the pattern of the gate layer is connected to a part of thepattern of the source-drain layer through the via hole.

Another embodiment of the invention provides an electronic apparatuscomprising the above thin film transistor or the above array substrate.

Another embodiment of the invention provides a method for manufacturinga thin film transistor, comprising:

preparing a mixture including a semiconductor nano-material and aphotoresist material;

applying the mixture over a substrate, and forming a patterned activelayer by exposure and development.

Preparing the mixture comprises:

mixing the semiconductor nano-material and the photoresist material witha solvent, and making a homogeneous mixture by stirring or ultrasonic;

or, dispersing the semiconductor nano-material in solvent in advance,and then, mixing uniformly the solvent mixed with the photoresistmaterial.

Comparing to prior arts, the technical solutions provided according theembodiments of the present invention described above have followingadvantage: patterned active layer is obtained by mixing thesemiconductor nano-material and the photoresist material, to disperseuniformly the nano-material in the photoresist material, by applying themixture on the substrate, and by exposing and developing. Thesemiconductor nano-material in the active layer can be connected eachother to form a plurality of electrical path. Therefore, according thepresent invention, the semiconductor nano-material can be used as anactive layer of a thin film transistor performed in simple and easymanner, thereby reducing producing cost of the TFT-LCD.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to clearly illustrate the technical solution of the embodimentsof the invention, the drawings of the embodiments will be brieflydescribed in the following; it is obvious that the described drawingsare only related to some embodiments of the invention and thus are notlimitative of the invention.

FIG. 1 is a schematic view of a thin film transistor provided accordingto an embodiment of the invention in an array substrate;

FIGS. 2a to 2f are schematic views of a manufacturing process of anarray substrate provided according to an embodiment of the presentinvention including thin film transistors;

FIG. 3 is a schematic view of an active layer in a thin film transistorprovided according to an embodiment of the present invention.

DETAILED DESCRIPTION

In order to make objects, technical details and advantages of theembodiments of the invention apparent, the technical solutions of theembodiment will be described in a clearly and fully understandable wayin connection with the drawings related to the embodiments of theinvention. It is obvious that the described embodiments are just a partbut not all of the embodiments of the invention. Based on the describedembodiments herein, those skilled in the art can obtain otherembodiment(s), without any inventive work, which should be within thescope of the invention.

A thin film transistor (TFT) provided according to the present inventionmay be applied to an array substrate of AMLCD or AMOLED, the thin filmtransistor may be a top gate type, a bottom gate type, etching stoptype, back channel etch type, coplanar type, or any other structuraltype. In the embodiments of the present invention, description is madeby take the bottom gate type thin film transistor as an example. Asillustrated in FIG. 1, the TFT comprises a gate electrode 21, a gateinsulating layer 3, an active layer 5, a source electrode 41, and adrain electrode 42, disposed on a base substrate 1. The active layer 5is formed of a mixture including a semiconductor nano-material and aphotoresist material. The semiconductor nano-material is, for example,one or more selected from a group consisting of a semiconductornano-wire, a carbon nanotube, and a semiconductor nanoscale graphene. Ifthe semiconductor nano-wire is used, it may be one or more selected froma group consisting of cadmium sulfide, zinc oxide, silicon, cadmium,gallium nitride, indium phosphide. The photoresist material is, forexample, an electron beam photoresist of polymethylmethacrylate (PMMA)or a photosensitive polyimide (PI).

Specifically, the mixture used in an embodiment of the present inventionis prepared by mixing the semiconductor nano-material in a liquidphotoresist material at some concentration ratio, and dispersinguniformly the semiconductor nano-material in the photoresist material byapplying a high power ultrasonic on or stirring the photoresist materialmixed with the semiconductor nano-material. Before the semiconductornano-material is mixed in the photoresist material, the semiconductornano-material may be diluted by using organic solvent, such as, benzene,ethanol, acetone, or the like, and then may be mixed in the photoresistmaterial to be stirred, so that it is easy to disperse the nano-materialuniformly in the photoresist material. Content of the semiconductornano-material in the mixture is, preferably from 1 mg/mL to 50 mg/mL;more preferably from 5 mg/mL to 30 mg/mL; most preferably from 10 mg/mLto 20 mg/m L. After the active layer is formed of the mixture, the massratio of the semiconductor nano-material to photoresist material is from1:5 to 1:250, preferably from 1:25 to 1:150, more preferably from 1:50to 1:100.

The semiconductor nano-material, such as carbon nano-tube, is dispersedin organic solvent, such as ethanol, and is mixed uniformly, and theorganic solvent mixed with the semiconductor nano-material is added intoliquid phase photoresist material, such as PMMA. By ultrasonic treatmentfor 10 to 60 minutes, the components are mixed uniformly. The mixtureincluding the semiconductor nano-material and photoresist material isapplied on a substrate to form an active thin film layer, then anexposure process is performed on the substrate. In the embodiment of theinvention, an electron beam positive photoresist of PMMA is adopted, andit is exposed by an electron beam. The film in the region exposed to theelectronic beam is removed by developing process, and the film in theun-exposed region is retained, i.e., a patterned active layer is formed.If other photoresist materials are used, the exposing manner, forexample, such as ultraviolet radiation exposing, may be selectedaccording to the property of the photoresist material.

According to another embodiment of the present invention, there isprovided an array substrate, including a base substrate 1, and a pixelelectrode 6 and the TFT as described above disposed on the basesubstrate 1. As illustrated in FIG. 1, an active layer 5 formed of amixture of semiconductor nano-material and photoresist material in theTFT is disposed on a gate insulating layer 3, the left part of theactive layer 5 in FIG. 1 is covered on the source electrode 41 and thedrain electrode 42 of the TFT, i.e., as the active layer of the TFT.Meanwhile, the pixel electrode 6 is disposed on the right part of theactive layer 5 in FIG. 1, the active layer 5 formed of the mixture ofthe semiconductor nano-material and photoresist material has a flatsurface, and thus, a planarization layer can be omitted, so that thepixel electrode 6 is disposed directly on the active layer 5. Further,since the active layer 5 is conductive per se, and electrical connectionbetween the drain electrode 42 and the pixel electrode 6 can beachieved, the step for etching a via hole in an insulating planarizationlayer in prior arts can be omitted.

That is to say, the active layer according to the embodiment of thepresent invention may have a flat surface, and thus, it has the functionof a planarization layer per se.

Furthermore, the array substrate further includes a pixel defining layer(PDL) 7 on the gate insulating layer 3, the pixel defining layer 7 islocated around the pixel electrode 6, to defined a region of pixelunits, and thus, the array substrate in the embodiments of the presentinvention can be applied to AMOLED.

Alternatively, a via hole 30 may be disposed in the gate insulatinglayer 3, a part of the gate layer pattern and a part of the source-drainlayer pattern may be connected by the via hole. When a circuit design onan array substrate is complicated, phenomena that a plurality ofelectrical conduct layers are arranged in cross are appeared. In theembodiments of the present invention, the gate layer pattern and a partof the source-drain layer are used as a conductive line, and theelectrical connection is created by the via hole 30 in the gateinsulating layer 3, thereby reducing the layer number of conductivelines, and simplifying manufacturing process of the array substrate.

According to still another embodiment of the present invention, there isprovided a method for manufacturing an array substrate, including:

S1: as illustrated in FIG. 2a , a gate layer pattern is formed on a basesubstrate 1, and the gate layer pattern includes a gate electrode 21.

Specifically, a gate layer is deposited on a base substrate 1, and then,a layer of photoresist is coated on the gate layer, after the process ofexposing and developing, a gate layer pattern is formed by wet etching,and removing the rest of the photoresist, finally, the gate layerpattern including a gate line (not illustrated in the drawings) and thegate electrode 21 is formed.

S2: a gate insulating layer is formed on the substrate.

S3: as illustrated in FIG. 2b , by a patterning process, a via hole 30is formed in the gate insulating layer 3.

Thus, a part of a source-drain layer pattern to be formed subsequentlyand a part of the gate layer pattern can be connected by the via hole30, thereby reducing layer number of conductive lines, and simplifyingmanufacturing process of the array substrate.

Of course, the present step S3 is an optional step, in the case thatcircuit design on the array substrate is simple per se, the present stepS3 can be omitted.

S4: as illustrated in FIG. 2c , a source-drain layer pattern is formedon the substrate, the source-drain layer pattern include a sourceelectrode and a drain electrode.

Specifically, a source-drain layer is deposited on the substrate, andthen, a layer of photoresist is coated on the source-drain layer, afterthe processes of exposing, developing, and the like, the source-drainlayer pattern is formed by using wet etch, and by removing the restphotoresist, the source-drain layer pattern including a data line (notillustrated in the drawings), the source electrode 41, and the drainelectrode 42 is finally formed, in which the source electrode 41 and thedrain electrode 42 are located on both sides of the gate electrode 21.

S5: as illustrated in FIG. 2d , an active layer 5 is formed on thesubstrate.

First, a mixture including a semiconductor nano-material and aphotoresist material is prepared. Specifically, mixing the semiconductornano-material and the photoresist material with a solvent, and making ahomogeneous mixture by stirring or ultrasonic; or, dispersing thesemiconductor nano-material in solvent in advance, and then, mixinguniformly the solvent mixed with the photoresist material.

Then, the prepared mixture is applied on the substrate, after exposing,developing, and the like, patterned active layer 5 is formed, and theactive layer 5 is covered on the source electrode 41 and the drainelectrode 42.

S6: as illustrated in FIG. 2e , a transparent electrode layer patternincluding a pixel electrode 6 is formed on the active layer 5.

Specifically, the transparent electrode layer is deposited on thesubstrate by using a sputtering technology, the material of thetransparent electrode layer is preferably indium tin oxide (ITO), then,a layer of photoresist is applied on the transparent electrode layer,after exposing, developing, and the like, the transparent electrodelayer pattern including the pixel electrode 6 is formed by using wetetching, and removing the rest photoresist, finally, the formed pixelelectrode 6 is located on the right part of the active layer 5.

The surface of the active layer 5 formed of the mixture of thesemiconductor nano-material and photoresist material is a flat surface,and therefore, a planarization layer can be omitted, and the pixelelectrode 6 can be disposed directly on the active layer 5. furthermore,since the active layer 5 may be conductive per se, and the electricalconnection between the drain electrode 42 and the pixel electrode 6 canbe achieved, the step for forming a via hole in insulating planarizationlayer in the prior arts is omitted.

Preferably, in the steps S4 and S6 described above, the source-drainlayer and the transparent electrode layer may be wet-etched by selectingthe same etching solution, and the etching solution should have aetching selectivity as high as possible to the transparent electrodelayer and the source-drain layer, so that the transparent electrodelayer is etched rapidly in the step S6, without influencing originalpattern of the source-drain layer. In this way, the same etchingsolution can be applied in both the steps S4 and S6, thereby simplifyingthe selecting of the etching solution.

After the transparent electrode layer pattern including the pixelelectrode 6 is formed on the active layer 5, the method may furtherinclude:

S7: as illustrated in FIG. 2f , a pixel defining layer (PDL) 7 is formedon the substrate.

Specifically, a thin film for the pixel defining layer is formed on thesubstrate, after exposing, developing, and the like, the pixel defininglayer 7 is obtained, after drying and solidification process, the pixeldefining layer 7 located around the pixel electrode 6 may be formed, todefine regions of the pixel units.

In the array substrate and the method for manufacturing the sameprovided according to the embodiments of the present invention, thesemiconductor nano-material and the photoresist material are mixed, sothat the semiconductor nano-material is dispersed uniformly in thephotoresist material, and the mixture is applied on the array substrateto form a thin film, after exposing, developing, and the like, thepatterned active layer is formed. The semiconductor nano-material in theactive layer can be connected together, as illustrated in FIG. 3, thesemiconductor nano-material may be connected in irregular curve manner,in order to form a plurality of electrical conductive paths, to act asthe active layer in the TFT. Therefore, the semiconductor nano-materialas the active layer in the TFT can be performed in simple and easymanner in the embodiments of the present invention, thereby reducing thecost of production of the TFT-LCD.

As described above, the thin film transistor and the method formanufacturing the same according to the embodiments of the presentinvention have been described taking a bottom gate type thin filmtransistor as an example, however, the present invention is not limitedto the bottom gate type thin film transistor. For other types of thinfilm transistor, any suitable position relations of the gate electrode,the gate insulating layer, the active layer, the source electrode anddrain electrode and the forming sequence for manufacturing process maybe adopted.

For example, in the case of the bottom gate type thin film transistor,the position relations of different layers can adopt the following ways:the gate insulating layer is located above the gate electrode, thesource electrode and the drain electrode are located above the gateinsulating layer and disposed on both sides of the gate electrode, theactive layer is located above the source electrode and the drainelectrode, and above the gate insulating layer. In the case of thebottom gate type thin film transistor used for the array substrate, thepixel electrode may be disposed directly on the active layer, therebyomitting a planarization layer.

According to further embodiment of the present invention, there isprovided an electronic apparatus, including the TFT and the arraysubstrate according to the embodiments of the present inventiondescribed above, the electronic apparatus may be any products orcomponents having a display function, such as, a liquid crystal panel,an electronic paper, an OLED panel, a liquid crystal TV, a liquidcrystal display, a digital camera, a mobile telephone, and a flatcomputer, or it may be an electronic apparatus such as a X-ray detector.

Since the electronic apparatus provided according to the embodiments ofthe present invention has the same technical features with the TFT andthe array substrate provided according to the embodiments invention asdescribed above, the same technical effects can be obtained, and thesame technical problems can be resolved.

The foregoing is merely exemplary embodiments of the invention, but isnot used to limit the protection scope of the invention. The protectionscope of the invention shall be defined by the attached claims.

What is claimed is:
 1. A method for manufacturing a thin filmtransistor, comprising: preparing a mixture including a semiconductornano-material and a photoresist material; and applying the mixture overa substrate, and forming a patterned active layer by exposure anddevelopment.
 2. The method according to claim 1, wherein, preparing themixture comprises: mixing the semiconductor nano-material and thephotoresist material with a solvent, and making a homogeneous mixture bystirring or ultrasonic; or, dispersing the semiconductor nano-materialin solvent in advance, and then, mixing uniformly the solvent mixed withthe photoresist material.
 3. The method according to claim 2, wherein,the photoresist material is an electron beam photoresist ofpolymethylmethacrylate or a photosensitive polyimide.
 4. The methodaccording to claim 1, wherein, the photoresist material is an electronbeam photoresist of polymethylmethacrylate or a photosensitivepolyimide.
 5. The method according to claim 4, wherein, a mass ratiobetween the semiconductor nano-material and the photoresist material is1:5 to 1:250.
 6. The method according to claim 1, wherein, a mass ratiobetween the semiconductor nano-material and the photoresist material is1:5 to 1:250.
 7. The method according to claim 2, wherein, a mass ratiobetween the semiconductor nano-material and the photoresist material is1:5 to 1:250.
 8. The method according to claim 3, wherein, a mass ratiobetween the semiconductor nano-material and the photoresist material is1:5 to 1:250.